In "vanishing twin" syndrome, when the fetal tissue is absorbed by the other twin (or placenta or the mother), what exactly takes place? How exactly is the other twin absorbed?

Answer by Judie Brown on 9/28/2012:

Dear Curious

Here is a medical explanation:

http://www.americanpregnancy.org/multiples/vanishingtwin.html

"The cause of vanishing twin syndrome is frequently unknown. Abnormalities that
result in the vanishing twin appear to be present from early in development rather
than from a sudden occurrence. Analysis of the placenta and/or fetal tissue
frequently reveals chromosomal abnormalities, while the surviving twin is usually
normal. Improper cord implantation may also be a cause."